I have some FileMaker databases being served for dev purposes and I keep bumping into occurrences where the database/file is locked and I can't make changes to it.
How can I determine what application is touching/using this file so I can kill it?
Have you tried using the terminal command
$ lsof 'Filename'
For a more detailed look at the file use
$ lsof | grep -f 'Filename'
Should give you the command that is using it and also the PID of that file
Try adding sudo. I set up a similar setup with the same file name, it would only appear if the file was open somewhere in a application. It didn't show up until I added the sudo tough.
sudo lsof | grep /path/to/file/Data.fmp12